If you're concerned about flames, don't do anything alone and have someone on standby ready to disconnect electrics and/or use a suitable fire extinguisher. It probably won't be needed, but if it is then you've got it to hand immediately.
An extremely brief hunt online pulled up this https://www.ebay.com...-P/263546247059 which I think is what you're after? If not, it might help find something. From the number of results from just typing in "Mustang II Fusible Link" suggests this is a fairly common, but not terminal, problem.